Hypothesis Claim Testing

1. At a large publishing company, the mean age of proofreaders is 36.2 years with a standard deviation of 3.7 years. Assuming the age is normally distributed, find the following:
a. If a proofreader is selected at random what is probability his/her age will be between 36 and 38 years.
b. If a random selected sample 20 proofreaders is selected, what is the probability the mean of the sample will be 37 years?

2. The growing season for a random sample of 28 cities were recorded, yielding a sample mean of 190.7 days and a standard deviation of 54.2 days. Estimate the true proportion mean length of the growing season with 90% confidence.

3. A survey of 50 people after their first hang gliding experience showed that 21 would not want to hang glide again
c. Find the 90% confidence interval for the true proportion of people who would not hang glide a second time.
d. If 325 people go hang gliding for the first time, estimate the largest number of people who would repeat the experience?

4. In a random sample of 70 bolts, the mean length was 1.25 inches and the standard deviation was 0.01 inch. Find the 95% confidence interval of the true mean length of the bolt.